Tyre Size Guide

How to Read a Trailer or Caravan Tyre Size

Your tyre size is printed on the sidewall of your current tyre. On trailer and caravan tyres it will look something like the example below. Always match this exactly when ordering a replacement.

Some tyres show two load index numbers, for example 185/70R13C 106/104N. The first number applies when the tyre is fitted as a single wheel, and the second when fitted as a twin.

Shop caravan and trailer tyres or trailer wheel and tyre assemblies.

How to Read a Quad, ATV or Turf Tyre Size

Quad, ATV and turf tyres use a different format to trailer tyres. The size is shown as three numbers, for example 25x8.00-12.

We do not recommend changing from the manufacturer's specified size, as this takes into account the load, speed and gearing of the vehicle.

Shop quad and ATV tyres or turf tyres.

How to Measure a Trailer Rim

To find the right trailer rim, you will need to know:

• Rim width and diameter, in inches.
• Stud count, the number of wheel studs, usually 4 or 5.
• PCD (pitch circle diameter), an imaginary circle formed through the centre of the rim's stud holes. Common trailer PCDs include 4 inch, 100mm, 112mm, 115mm, 5.5 inch and 6.5 inch.
• Centre bore, the diameter of the hole in the centre of the rim.
• Offset (ET), how far the mounting face sits from the centre line of the rim.

What's stamped on the rim?

Rim width, diameter and offset are often stamped onto the rim, and will look something like 5.5Jx12 ET0. In this example, 5.5 is the rim width in inches, 12 is the diameter in inches and ET0 is the offset. PCD and centre bore generally need to be measured.

Measuring PCD

Measurement practices vary depending on the number of studs.

Shop trailer rims.

Tyre Speed Ratings

The speed rating is the letter at the end of the tyre size. It shows the maximum speed the tyre is designed for.

Tyre Load Ratings

The load index is the number before the speed rating. It shows the maximum load each tyre can carry.